Maltol is a naturally occurring substance found in the bark of young larch trees, pine needles and chicory. Early commercial production was from the destructive distillation of wood. Synthesis of maltol from 3-hydroxy-2-(1-piperidylmethyl)-1,4-pyrone was reported by Spielman and Freifelder in J. Am. Chem. Soc., 69, 2908 (1947). Schenck and Spielman, J. Am. Chem. Soc., 67, 2276 (1945), obtained maltol by alkaline hydrolysis of streptomycin salts. Chawla and McGonigal, J. Org. Chem. 39, 3281 (1974) and Lichtenthaler and Heidel, Angew. Chem., 81, 998 (1969), reported the synthesis of maltol from protected carbohydrate derivatives. Shono and Matsumura, Tetrahedron Letters No. 17, 1363 (1976), described a five step synthesis of maltol starting with methyl furfuryl alcohol.
The isolation of 6-methyl-2-ethyl-3-hydroxy-4H-pyran-4-one as one of the characteristic sweet-aroma components in refinery final molasses was reported by Hiroshi Ito in Agr. Biol. Chem., 40 (5), 827-832 (1976). This compound was previously synthesized by the process described in U.S. Pat. No. 3,468,915.
Syntheses of gamma-pyrones such as pyromeconic acid, maltol, ethyl maltol and other 2-substituted-3-hydroxy-gamma-pyrones are described in U.S. Pat. Nos. 3,130,204; 3,133,089; 3,140,239; 3,159,652; 3,365,469; 3,376,317; 3,468,915; 3,440,183; and 3,446,629.
Maltol and ethyl maltol enhance the flavor and aroma of a variety of food products. In addition, these materials are used as ingredients in perfumes and essences. The 2-alkenylpyromeconic acids reported in U.S. Pat. No. 3,644,635 and the 2-arylmethylpyromeconic acids described in U.S. Pat. No. 3,365,469 inhibit the growth of bacteri and fungi and are useful as flavor and aroma enhancers in foods and beverages and aroma enhancers in perfumes.